The nematode Caenorhabditis elegans is a choice model system for the study of the genetic control of cell differentiation. Genes involved in the cell-specific differentiation of two identified cell in C. elegans (the touch cells and the D cells) will be characterized through the isolation of mutants affected in the function and development of these cells or their precursors. The specific aims of this proposal are: 1. to extend the existing genetic and ultrastructural analysis of the touch cells by isolating new alleles of existing genes (e.g. ts and null alleles) and alleles in new genes affecting the development of these cells; 2. to characterize wild-type touch cell development a) by electron microscopy to determine the sequence of events during cell maturation and b) by laser ablation to examine the involvement of other cells in this development; 3. to examine the expression of touch cell-specific genes in poly ploid cells generated by mutation and laser fusion; 4. to isolate and characterize mutations affecting D cell development. The fundamental approach is to use mutations to dissect the events in the differentiation of identified cells. The comparison of the mutations affecting these two different cell types allows an analysis of the types of developmental strategies used in C. elegans. The health relatedness of this work derives from its contribution to an understanding of basic cellular and developmental control mechanisms used in higher organisms and perhaps man.